Abstract: To improve the electrical withstand of a low voltage circuit breaker for high currents having multiple contacts of the same length and a stationary arc guiding horn having an intermediate edge extending over a short distance in the direction of movement of the front extensions of the contact fingers, a stationary arcing contact is arranged between the edge of the arc guiding horn and the stationary main contact. The stationary main contact is designed to cooperate with a movable arcing contact of at least one contact finger. At the beginning of the opening travel, closing of the arcing contacts takes place before the main contacts separate. The stationary arcing contact is located in the immediate vicinity of the edge.

Abstract: A limiting circuit breaker with a molded case comprises an overpressure actuator which, when an overpressure occurs in the arc extinguishing chamber due to the action of an arc drawn by the electrodynamic repulsion of the contacts, brings about actuation by a piston, subjected to this overpressure, of the circuit breaker trip bar. The overpressure actuator forms an almost leaktight assembly.